Aluminum-driven lattice-regulated high-performance layered sodium-ion battery cathode material, and preparation method and application thereof

Abstract

The application relates to the technical field of sodium ion battery positive electrode materials, in particular to an aluminum-driven lattice-regulated high-performance layered sodium ion battery positive electrode material and a preparation method and application thereof, and comprises the following steps: sequentially dissolving sodium acetate, aluminum nitrate, ferric nitrate, manganese sulfate and copper nitrate in deionized water, adding a modified liquid to form a solution A after mixing, dissolving citric acid in deionized water to form a solution B, adding the solution B into the solution A drop by drop to carry out a gel reaction to obtain a mixed solution, stirring and reacting for 4-5 hours to obtain a gel, carrying out drying treatment on the gel, grinding, pre-sintering, tabletting and then high-temperature calcining to obtain an aluminum-doped layered sodium ion battery positive electrode material. 3+ The Al-O bond energy formed with oxygen is significantly higher than that of the transition metal-oxygen bond, can serve as a structural anchor point in the lattice skeleton, inhibits the Jahn-Teller distortion, layer slip and phase change of transition metal ions in the charging and discharging process, and avoids lattice collapse and structure pulverization.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery cathode material technology, specifically to a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation, its preparation method, and its application. Background Technology

[0002] With the rapid development of renewable energy and large-scale energy storage technologies, higher requirements have been placed on secondary battery systems that are highly safe, low-cost, and resource-sustainable. Sodium-ion batteries are considered an important supplement to lithium-ion batteries in the field of large-scale energy storage due to the abundance of sodium resources, low cost, and environmental friendliness. Layered transition metal oxides have become a research hotspot for sodium-ion battery cathode materials due to their high theoretical specific capacity and good structural designability. Layered transition metal oxides are mainly divided into P2 type and O3 type. P2 type oxides can maintain the integrity of the structure and a low diffusion energy barrier, exhibiting better cycle stability and rate performance.

[0003] Existing layered sodium-ion battery materials are prone to irreversible phase transitions and lattice collapse, have slow sodium-ion diffusion kinetics, and are susceptible to side reactions and surface structure degradation at high voltage ranges. To address these issues, this invention proposes an aluminum-driven lattice-controlled high-performance layered sodium-ion battery cathode material, its preparation method, and its applications. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation, its preparation method, and its application, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation includes the following steps:

[0007] S1. Dissolve sodium acetate, aluminum nitrate, ferric nitrate, manganese sulfate and copper nitrate in deionized water in sequence, and continue to add the modified solution to form solution A. Dissolve citric acid in deionized water to form solution B.

[0008] S2. Add solution B dropwise to solution A to obtain a mixed solution, and stir the mixture at 300-500 r / min at 60-90℃ for 4-5 hours to obtain a gel.

[0009] S3. The gel is dried to obtain a precursor. The precursor is ground, pre-calcined, pressed into a sheet, and then calcined at high temperature to obtain an aluminum-doped layered sodium-ion battery cathode material.

[0010] The modified liquid is prepared through the following steps:

[0011] S11. Add the chloride salt product, trimethyl borate, and p-toluenesulfonic acid to anhydrous toluene and reflux at 100-110℃ for 5-6 hours.

[0012] S12. After the reaction is complete, toluene and excess trimethyl borate are removed by rotary evaporation to obtain an intermediate. The intermediate is then dissolved in deionized water to obtain an intermediate solution.

[0013] S13. Dissolve sodium tetrafluoroborate in deionized water and then add it dropwise to the intermediate solution. Stir at room temperature for 5-6 hours. After the reaction is complete, concentrate under reduced pressure at 40-50℃ to 30-40% of the original volume. Cool to 0-5℃ and let it stand to crystallize for 10-12 hours. Filter and wash the filter cake 2-3 times with deionized water. Dry under vacuum to obtain the modified ionic compound. Add the modified ionic compound to deionized water to obtain the modified solution.

[0014] Furthermore, the chloride product in step S11 is obtained through the following steps:

[0015] S111. After mixing choline chloride and ethylene glycol, add N-methylimidazole and 3-chloropropionic acid, stir for 5-10 min, add aluminum nitrate nonahydrate and stir until dissolved, and microwave at 90-95℃ for 2-3 h.

[0016] S112. After the reaction is complete, add anhydrous ethanol to dilute, stir for 10-15 min, remove ethanol by rotary evaporation to obtain crude product, wash crude product with ethyl acetate 3-4 times, and dry under vacuum to obtain chloride product.

[0017] Furthermore, in step S1, the mass ratio of sodium acetate, aluminum nitrate, ferric nitrate, manganese sulfate, copper nitrate, deionized water, and modified solution is 1:(0.02-0.15):(0.2-0.5):(0.3-0.6):(0.05-0.2):(5-15):(0.8-2), the mass ratio of citric acid to deionized water is 1:(15-20), and the mass ratio of solution A to solution B in step S2 is 1:(0.6-1.2).

[0018] Furthermore, in step S11, the mass ratio of chloride product, trimethyl borate, p-toluenesulfonic acid, and anhydrous toluene is 1:(1.5-3):(0.05-0.15):(15-20).

[0019] Furthermore, in step S12, the mass ratio of deionized water to the intermediate is (10-15):1.

[0020] Furthermore, in step S13, the mass ratio of the intermediate solution, sodium tetrafluoroborate, and deionized water is 1:(0.4-0.8):(6-15), and the mass ratio of the modified ionic compound to deionized water is 1:(5-15).

[0021] Furthermore, the mass ratio of choline chloride, ethylene glycol, N-methylimidazole, 3-chloropropionic acid, aluminum nitrate nonahydrate and anhydrous ethanol in step S111 is 1:(2-4):(0.6-1.2):(0.7-1.3):(0.03-0.1):(20-25).

[0022] Furthermore, in step S3, the grinding time is 25-30 min, the sieve type is 200-250 mesh, and the pressure is 10-12 MPa; the pre-calcination temperature is 450-480℃, and the holding time is 3-6 h; the high-temperature calcination in step S3 is a two-stage process, specifically: first, the temperature is raised to 350-550℃ and held for 5-7 h, with a heating rate of 2-7℃ / min; then, the temperature is raised to 850-950℃ and held for 10-15 h.

[0023] Furthermore, a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation is prepared according to any one of the preparation methods described above.

[0024] Furthermore, the application of the aforementioned aluminum-driven lattice-controlled high-performance layered sodium-ion battery cathode material in sodium-ion batteries.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. This invention utilizes Al 3+ The Al-O bond formed with oxygen has a significantly higher bond energy than the transition metal-oxygen bond. It can act as a structural anchor point in the crystal lattice framework, suppressing the Jahn-Teller distortion, lamination slip, and phase transitions (such as the irreversible P2 / O3 phase transition) of transition metal ions during charging and discharging. This avoids lattice collapse and structural pulverization, fundamentally improving the structural reversibility of the material. Aluminum doping can stabilize the valence state evolution behavior of transition metals by regulating the distribution of electron clouds in the crystal lattice, suppressing excessive oxidation / reduction, dissolution, and electrolyte side reactions of transition metals under high voltage, reducing interfacial impedance growth and loss of active materials, and significantly extending the cycle life of the material.

[0027] 2. This invention utilizes Al 3+The synergistic effect of doping and modified ionic compounds enables precise control of the interlayer lattice spacing, ensuring the integrity of the layered structure while providing a more spacious and stable two-dimensional migration channel for sodium ions. This reduces the steric hindrance during sodium ion insertion / extraction. The synergistic effect of the stable lattice structure and optimized ion channels significantly reduces the diffusion barrier of sodium ions, enabling the material to maintain high ion transport efficiency even at high current densities. This solves the problem of "poor rate performance and sharp capacity drop at high rates" in traditional layered materials. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the preparation process of the aluminum-doped layered sodium-ion battery cathode material in this invention;

[0029] Figure 2 This is a schematic diagram of the preparation process of the modified liquid in this invention;

[0030] Figure 3 This is a schematic diagram of the preparation process of chloride products in this invention;

[0031] Figure 4 These are XRD patterns of Comparative Example 1 and Examples 1-3 of the present invention;

[0032] Figure 5 Figure 1 shows the surface SEM images of the aluminum-doped layered sodium-ion battery cathode material prepared in Example 1 of this invention. Figure 1(a) is a 30 μm low-rate panoramic view, Figure 1(b) is a 5 μm medium-rate detail view, and Figure 1(c) is a 500 nm high-rate close-up view.

[0033] Figure 6 The rate profiles of the coin cells prepared in Comparative Example 1 and Examples 1-3 of this invention are shown.

[0034] Figure 7 The following are cycling diagrams of the coin cells prepared in Comparative Example 1 and Examples 1-3 of this invention at a current density of 1C.

[0035] Figure 8 This is a cycling diagram of the coin cell prepared in Example 2 of the present invention at a current density of 10C;

[0036] Figure 9 The images show the XRD patterns of the coin cells prepared in Comparative Example 1 and Example 1 before and after 100 cycles. Figure a shows the XRD pattern of the coin cells prepared in Comparative Example 1 before and after 100 cycles, and Figure b shows the XRD pattern of the coin cells prepared in Example 1 before and after 100 cycles.

[0037] Figure 10 These are diagrams showing the mixed solution, gel, and the state of the gel after drying, formed during the preparation of the aluminum-doped layered sodium-ion battery cathode material of this invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] Please see Figures 1-10 The present invention provides a technical solution:

[0040] Example 1:

[0041] A method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation includes the following steps:

[0042] I. Preparation of chloride salt products:

[0043] S111. Mix 10.0g choline chloride and 20.0g ethylene glycol, add 6.0g N-methylimidazole and 7.0g 3-chloropropionic acid, stir for 5min; add 0.3g aluminum nitrate nonahydrate to dissolve, and microwave at 90℃ for 2h.

[0044] S112. After the reaction is complete, add 200.0 g of anhydrous ethanol to dilute, stir for 10 min, place in a rotary evaporator, and evaporate at 35 °C and 120 rpm to remove low-boiling-point ethanol solvent; wash the crude product three times with ethyl acetate and dry under vacuum to obtain the chloride product.

[0045] II. Preparation of the modified solution:

[0046] S11. Take 5.0g of chloride product, 7.5g of trimethyl borate, 0.25g of p-toluenesulfonic acid, and 75.0g of anhydrous toluene, and reflux at 100℃ for 5h.

[0047] S12. In a rotary evaporator, rotary evaporation is carried out at 45℃ and 120 rpm to remove toluene and excess trimethyl borate, and an intermediate is obtained. 5.0 g of the intermediate is dissolved in 50.0 g of deionized water to obtain an intermediate solution.

[0048] S13. Take 4.0g of sodium tetrafluoroborate and add it to 60.0g of deionized water. Mix the mixture and then add it dropwise to 10.0g of intermediate solution. Stir at room temperature for 5h. After the reaction is complete, concentrate the mixture under reduced pressure at 40℃ to 30% of the original volume. Cool the mixture to 0℃ and let it stand for 10h to crystallize. Filter the mixture and wash the filter cake twice with deionized water. Dry the mixture under vacuum to obtain the modified ionic compound. Take 1g of the modified ionic compound and add it to 5g of deionized water to prepare the modified solution.

[0049] III. Preparation of cathode materials:

[0050] S1. Take 10.0g sodium acetate, 0.2g aluminum nitrate, 2.0g ferric nitrate, 3.0g manganese sulfate, and 0.5g copper nitrate, dissolve them in 50g deionized water, and add 8.0g of modifying solution to mix and obtain solution A; take 10.0g citric acid and dissolve it in 150.0g deionized water to obtain solution B.

[0051] S2. Take 6.0g of solution B and add it dropwise to 10.0g of solution A to obtain a mixed solution. Stir the mixture at 60℃ and 300r / min for 4h to obtain a gel.

[0052] S3. The precursor was obtained by vacuum drying the gel at 80℃ for 12h; grinding for 25min and passing it through a 200-mesh sieve; pressing it into tablets at 10MPa; pre-calcining at 450℃ for 3h; two-stage calcination: holding at 350℃ for 5h (heating rate 2℃ / min) and then heating to 850℃ for 10h, followed by natural cooling to obtain aluminum-doped layered sodium-ion battery cathode material.

[0053] Example 2:

[0054] A method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation includes the following steps:

[0055] I. Preparation of chloride salt products:

[0056] S111. Mix 10.0g choline chloride and 30.0g ethylene glycol, add 9.0g N-methylimidazole and 10.0g 3-chloropropionic acid, stir for 8 minutes; add 0.6g aluminum nitrate nonahydrate to dissolve, and microwave at 93℃ for 2.5 hours.

[0057] S112. After the reaction is complete, add 230.0 g of anhydrous ethanol to dilute, stir for 13 min, place in a rotary evaporator, and evaporate at 35 °C and 120 rpm to remove low-boiling-point ethanol solvent; wash the crude product three times with ethyl acetate and dry under vacuum to obtain the chloride product.

[0058] II. Preparation of the modified solution:

[0059] S11. Take 5.0g of chloride product, 10.0g of trimethyl borate, 0.5g of p-toluenesulfonic acid, and 85.0g of anhydrous toluene, and reflux at 105℃ for 5.5h.

[0060] S12. In a rotary evaporator, rotary evaporation is carried out at 45℃ and 120 rpm to remove toluene and excess trimethyl borate, yielding an intermediate; 5.0 g of the intermediate is dissolved in 60.0 g of deionized water to obtain an intermediate solution.

[0061] S13. Take 6.0g of sodium tetrafluoroborate and add it to 100.0g of deionized water. Mix the mixture and then add it dropwise to 10.0g of intermediate solution. Stir at room temperature for 5.5h. After the reaction is complete, concentrate the mixture under reduced pressure at 45℃ to 35% of the original volume. Cool the mixture to 3℃ and let it stand for 11h to crystallize. Filter the mixture and wash the filter cake twice with deionized water. Dry the mixture under vacuum to obtain the modified ionic compound. Take 1g of the modified ionic compound and add it to 10g of deionized water to prepare the modified solution.

[0062] III. Preparation of cathode materials:

[0063] S1. Take 10.0g sodium acetate, 0.9g aluminum nitrate, 3.5g ferric nitrate, 4.0g manganese sulfate, and 1.3g copper nitrate, dissolve them in 100.0g deionized water, and add 13.0g of modified solution to mix and obtain solution A; take 10.0g citric acid and dissolve it in 180.0g deionized water to obtain solution B.

[0064] S2. Take 9.0g of solution B and add it dropwise to 10.0g of solution A to obtain a mixed solution. Stir the mixture at 75℃ and 400r / min for 4.5h to obtain a gel.

[0065] S3. The precursor was obtained by vacuum drying the gel at 80℃ for 12h; grinding for 28min and passing it through a 230-mesh sieve; pressing it into tablets at 11MPa; pre-calcining at 465℃ for 4.5h; two-stage calcination: holding at 450℃ for 6h (heating rate 5℃ / min) and then heating to 900℃ and holding for 13h, followed by natural cooling to obtain aluminum-doped layered sodium-ion battery cathode material.

[0066] Example 3:

[0067] A method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation includes the following steps:

[0068] I. Preparation of chloride salt products:

[0069] S111. Mix 10.0g choline chloride and 40.0g ethylene glycol, add 12.0g N-methylimidazole and 13.0g 3-chloropropionic acid, stir for 10min; add 1.0g aluminum nitrate nonahydrate to dissolve, and microwave at 95℃ for 3h.

[0070] S112. After the reaction is complete, add 250.0 g of anhydrous ethanol to dilute, stir for 15 min, place in a rotary evaporator, and evaporate at 35 °C and 120 rpm to remove low-boiling-point ethanol solvent; wash the crude product with ethyl acetate 4 times and dry under vacuum to obtain the chloride product.

[0071] II. Preparation of the modified solution:

[0072] S11. Take 5.0g of chloride product, 15.0g of trimethyl borate, 0.75g of p-toluenesulfonic acid, and 100.0g of anhydrous toluene, and reflux at 110℃ for 6h.

[0073] S12. In a rotary evaporator, rotary evaporation is carried out at 45℃ and 120 rpm to remove toluene and excess trimethyl borate, and an intermediate is obtained. 5.0 g of the intermediate is added to 75.0 g of deionized water to dissolve and obtain an intermediate solution.

[0074] S13. Take 8.0g of sodium tetrafluoroborate and add it to 150.0g of deionized water. Mix the mixture and then add it dropwise to 10.0g of intermediate solution. Stir at room temperature for 6 hours. After the reaction is complete, concentrate the mixture under reduced pressure at 50℃ to 40% of the original volume. Cool the mixture to 5℃ and let it stand for 12 hours to crystallize. Filter the mixture and wash the filter cake three times with deionized water. Dry the mixture under vacuum to obtain the modified ionic compound. Take 1g of the modified ionic compound and add it to 15g of deionized water to prepare the modified solution.

[0075] III. Preparation of cathode materials:

[0076] S1. Take 10.0g sodium acetate, 1.5g aluminum nitrate, 5.0g ferric nitrate, 6.0g manganese sulfate, and 2.0g copper nitrate, dissolve them in 150.0g deionized water, and add 20.0g of modified solution to obtain solution A; take 10.0g citric acid and dissolve it in 200.0g deionized water to obtain solution B.

[0077] S2. Take 12.0g of solution B and add it dropwise to 10.0g of solution A to obtain a mixed solution. Stir the mixture at 90℃ and 500r / min for 5h to obtain a gel.

[0078] S3. The precursor was obtained by vacuum drying the gel at 80℃ for 12h; grinding for 30min and passing it through a 250-mesh sieve; pressing it into tablets at 12MPa; pre-calcining at 480℃ for 6h; two-stage calcination: holding at 550℃ for 7h (heating rate 7℃ / min) and then heating to 950℃ for 15h, followed by natural cooling to obtain aluminum-doped layered sodium-ion battery cathode material.

[0079] Comparative Example 1

[0080] Comparative Example 1 differs from Example 1 in that no aluminum source is added, and the modified liquid is replaced with an equal mass of a common solvent (composed of ethyl acetate, deionized water, and citric acid). The remaining steps are exactly the same as in Example 1.

[0081] Comparative Example 2

[0082] Comparative Example 2 differs from Example 1 in that the modified liquid is replaced with an equal mass of a common solvent (composed of ethyl acetate, deionized water, and citric acid), while the remaining steps are exactly the same as in Example 1.

[0083] Comparative Example 3

[0084] Comparative Example 3 differs from Example 1 in that the chloride product is replaced with an equal mass of choline chloride-ethylene glycol eutectic solvent, and the remaining steps are exactly the same as in Example 1.

[0085] The sodium-ion battery cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 were weighed with polyvinylidene fluoride binder and acetylene black conductive agent at a mass ratio of 8:1:1 and placed in a ball mill jar. An appropriate amount of N-methyl-2-pyrrolidone was added as a dispersion solvent, and the mixture was ball milled at 500 rpm for 3 hours to obtain a uniform and fine electrode slurry. The slurry was uniformly coated on an aluminum foil current collector and transferred to a vacuum drying oven. The slurry was vacuum dried at 80°C for 12 hours to completely remove the solvent. The dried electrode was then cut into circular working electrodes with a diameter of 10 mm.

[0086] Battery assembly was carried out in an argon atmosphere glove box with water and oxygen content both <0.1ppm. The CR2025 coin cell was assembled in the following order: positive electrode shell, working electrode, Whatman glass fiber separator, drop-in NaClO4 / EC electrolyte, sodium sheet negative electrode, nickel foam, and negative electrode shell. The cells were sealed using a battery packaging machine under a pressure of 0.5MPa. After assembly, the cells were allowed to stand for more than 10 hours to allow the electrolyte to fully wet the electrode materials. Then, the electrochemical performance of the assembled coin cells was tested.

[0087] 0.1C discharge specific capacity test: The first discharge specific capacity was tested by constant current charging and discharging at a current density of 0.1C, and the data was recorded.

[0088] 1C discharge specific capacity test: Switch to 1C current density constant current charge and discharge, test the stable discharge specific capacity, and record the data.

[0089] 100-cycle performance test: Maintain a current density of 1C for 100 consecutive cycles, record the discharge capacity of each cycle, and calculate the capacity retention rate after 100 cycles (capacity retention rate = discharge capacity of the 100th cycle / discharge capacity of the first cycle × 100%). The specific test results are shown in Table 1 below:

[0090] Table 1

[0091]

[0092] As shown in Table 1, the aluminum-driven lattice-controlled layered sodium-ion battery cathode materials prepared in Examples 1-3 exhibit significantly better electrochemical performance than the comparative materials without aluminum doping, without modified solutions, and without chloride products. The 0.1C discharge specific capacity, 1C discharge specific capacity, and capacity retention after 100 cycles of Examples 1-3 are all much higher than those of the comparative examples. Example 2 shows the best overall performance, while Examples 1 and 3 have similar performance and are significantly better than the comparative examples. Comparative example 1, lacking an aluminum source, cannot achieve lattice control, and the modified solution was replaced with a common solvent, completely losing the synergistic effect of the modified ionic compound, resulting in a significant decrease in structural stability and ion transport capacity. Although comparative example 2 added an aluminum source, it did not use a modified solution, and the common solvent could not provide the key functions of the modified ionic compound in promoting uniform doping, stabilizing lattice shrinkage, and optimizing ion channels during the gel reaction. Therefore, the regulatory effect of aluminum was not fully utilized, resulting in limited performance improvement. Comparative example 3 replaced the chloride product with a common eutectic solvent, leading to abnormal structures in the subsequently synthesized modified ionic compounds, which could not react with Al. 3+ An effective synergistic regulation system is formed. Even in the presence of an aluminum source, the lattice disorder remains high, and the capacity decay accelerates. The above results fully demonstrate that aluminum doping and modified ionic compounds synergistically regulate the lattice, which can significantly improve the specific capacity, rate performance, and long-cycle stability of the cathode material, with outstanding effects.

[0093] Figure 4 The XRD patterns of Comparative Example 1 and Examples 1-3 of this invention show that the characteristic diffraction peaks of all samples (Examples 1-3 and Comparative Example 1) correspond one-to-one with the peak positions of standard PDF card #O3: 00-053-0349 (layered oxide O3 phase), with no additional impurity peaks. This proves that all samples are pure O3-type layered oxides without impurity phase formation and good crystallinity. Furthermore, the absence of sodium aluminate impurity peaks corresponding to PDF#NaAlO2: 33-120 in the spectra indicates that aluminum is not present as an impurity phase but has been successfully doped into the main crystal lattice. The characteristic peaks of Examples 1-3 (Al doping and modification liquid synergy) are significantly more intense and sharper, indicating that Al doping greatly improves the crystallinity and structural order of the material. The characteristic peaks of the examples show a slight shift towards the higher 2θ direction, directly proving that Al... 3+ The metal ions in the crystal lattice were successfully replaced, inducing lattice contraction and achieving structural control; while Comparative Example 1, due to the lack of an aluminum source and the replacement of the modification solution with a common solvent, lacked Al. 3+ The structure anchoring effect is lacking, and the optimization effect of modified ionic compounds on the distribution of lattice electron clouds and ion channels is also lacking, resulting in high lattice disorder and poor stability of layered structure. Its XRD characteristic peak intensity is significantly lower than that of the example, and the structure deteriorates severely after cycling.

[0094] Figure 5Figure 1 shows the surface SEM images of the aluminum-doped layered sodium-ion battery cathode material prepared in Example 1 of this invention. Figure (a) is a low-rate panoramic view, showing uniform particle distribution and size, with no obvious large agglomerates or abnormally large particles, exhibiting good dispersibility. The material consists of spherical / near-spherical secondary particles with particle sizes concentrated in the micrometer range, providing good flowability and compaction for subsequent electrode processing. This demonstrates that the preparation process can stably produce powders with uniform morphology and no batch-to-batch morphological differences. Figure (b) shows a medium-rate detail, where the secondary particles are formed by the agglomeration of primary grains. The particle surfaces are rough and porous, indicating that the material has abundant pores. The secondary particle size is approximately 1-3 μm, while the primary grain size is in the sub-micrometer range. Micrometer-scale, conforming to the typical morphology of layered oxide cathode materials, the porous structure increases the contact area between the electrolyte and the material, shortens the sodium ion diffusion path, and improves rate performance; at the same time, it buffers the volume expansion during charge and discharge, improving cycle stability. Figure (c) shows a close-up of the primary grain morphology at high rate: the primary grains are regular polygonal / plate-like structures with clear crystal faces, high crystallinity, dense particle surfaces, no obvious cracks or pores, and good structural integrity; at the same time, nanoscale pores are retained, balancing structural stability and ion transport efficiency. Aluminum doping does not destroy the intrinsic morphology of the grains, but rather optimizes grain growth, making the grain boundaries clearer and the structure denser, further improving the structural stability of the material.

[0095] Figure 6 The figures show the rate performance of the coin cells prepared in Comparative Example 1 and Examples 1-3 of this invention. Examples 1-3, modified with Al doping, exhibited significantly better specific capacities than the undoped Comparative Example 1 across the entire rate range of 0.1-10C, demonstrating that Al doping can significantly improve the rate performance of the material. At an ultra-high rate of 10C, the capacity of the examples was 1.5-1.8 times that of Comparative Example 1, indicating that Al doping significantly accelerated the diffusion kinetics of sodium ions, making it suitable for fast-charging applications. In the rate recovery test, the capacity of the examples was almost completely reversible, while Comparative Example 1 experienced irreversible capacity loss, confirming that Al doping effectively stabilized the lattice and suppressed structural degradation. Example 2 showed the best rate performance, indicating that this doping amount achieved the optimal balance between capacity and rate, representing the optimal doping ratio.

[0096] Figure 7 The figures show the cycling performance of the coin cells prepared in Comparative Example 1 and Examples 1-3 at a current density of 1C. Aluminum doping (Examples 1-3) effectively suppressed capacity decay during cycling, and the capacity retention after 100 cycles was significantly higher than that of the undoped Comparative Example 1. This confirms that Al doping... 3+Doping can significantly stabilize the lattice structure of materials and prevent phase transitions and structural collapse during charging and discharging. Example 2 showed comprehensive advantages in both initial capacity and cycle stability, indicating that an appropriate amount of Al doping (the ratio in Example 2) achieved the best balance between structural stability and electrochemical activity. This result is in high agreement with the previous XRD (lattice shrinkage / structural stability) and SEM (dense morphology / defect-free) analyses, further confirming the effectiveness and rationality of aluminum doping modification from the perspective of electrochemical performance.

[0097] Figure 8 The graph shows the cycling performance of the coin cell prepared in Example 2 of this invention at a current density of 10C. Example 2 cycled 100 times at an ultra-high rate of 10C, with a capacity retention of approximately 74%, demonstrating excellent dual performance of fast charging and long cycling. This proves that aluminum doping modification endows the material with excellent structural stability and rapid ion transport capability. The curve shows no capacity drop throughout, indicating that the material lattice remains stable during continuous charging and discharging at high current, without irreversible phase transitions or electrode pulverization, thus verifying the protective effect of doping modification on the structure.

[0098] Figure 9 The images show the XRD patterns of the coin cells prepared in Comparative Example 1 and Example 1 before and after 100 cycles. Comparative Example 1 (Figure a) shows structural degradation. Before cycling (green curve, Pristine), the characteristic peaks are sharp and intense, indicating good crystallinity and a typical layered oxide structure. After 100 cycles (red curve, After 100 cycles), the intensity of all characteristic peaks decreases significantly, indicating that the long-range order of the crystal is severely damaged, the crystallinity decreases significantly, and some peaks disappear or broaden, indicating that the material has undergone an irreversible phase transition, the layered structure has collapsed, and even a tendency towards amorphization has emerged. The undoped Comparative Example 1 showed severe crystal structure degradation during cycling, unable to maintain its initial layered structure. The layered structure is the fundamental reason for its rapid degradation in cycling performance. The structural stability of Example 1 (Figure b) shows that before cycling (green curve, Pristine), the characteristic peaks are sharp and have high intensity, indicating good crystallinity. After 100 cycles (red curve, After 100 cycles), the position, number, and relative intensity of all characteristic peaks remain basically unchanged, without obvious peak shift, broadening, or disappearance. The peak intensity only decreases slightly, indicating that the long-range order of the crystal is effectively preserved and the layered structure does not undergo irreversible collapse. During the cycling process, the crystal structure of aluminum-doped Example 1 remains stable, effectively suppressing phase transitions and structural degradation, which explains its excellent cycling stability from a structural perspective.

[0099] Comparing the two spectra, the structural changes in Example 1 before and after the cycle are much smaller than those in Comparative Example 1, proving that Al 3+Successful doping stabilized the layered lattice, suppressing irreversible phase transitions and structural collapse during charge and discharge. The XRD results perfectly corroborate the excellent performance of Example 1 in long-term cycling at 1C and 10C, explaining the fundamental reason for its high capacity retention and absence of sudden decay, forming a complete logical chain of "structure-performance". Al 3+ After entering the crystal lattice, the layered structure is stabilized by the stronger Al-O bonds, which improves the structure's resistance to distortion. This modification mechanism has been directly verified by experiments.

[0100] Figure 10 The images show the mixed solution, gel, and the state of the gel after drying during the preparation of the aluminum-doped layered sodium-ion battery cathode material of this invention. The first stage is the mixed solution, which is a uniform and transparent orange-yellow solution in the beaker. There is no precipitation or layering. All metal salt precursors (sodium source, transition metal source, and aluminum source) have been completely dissolved and mixed evenly, forming a molecularly uniform solution system. Each component is uniformly dispersed at the atomic level in the solution, which lays the foundation for the uniform distribution of subsequent doping elements.

[0101] The second stage is the gel-gel transition. The solution transforms into a viscous, light brown gel-like substance, loses its fluidity, and becomes semi-solid. The precursor solution undergoes a hydrolysis-condensation reaction, forming a wet gel with a three-dimensional network structure. The formation of the gel indicates that the reaction process is controllable. Metal ions are uniformly encapsulated in the gel network, avoiding component segregation during the subsequent drying process.

[0102] The third stage is gel drying. After drying, the wet gel forms a porous, fluffy, yellowish-brown dry gel precursor with a distinct honeycomb-like pore structure. During the drying process, the solvent evaporates, forming a porous structure. This structure can effectively alleviate the volume shrinkage during the subsequent high-temperature calcination process and prevent powder agglomeration. The fluffy porous precursor increases the specific surface area, which is conducive to the diffusion of oxygen during calcination, ensuring that the precursor is fully oxidized and forming the pure phase target product.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice modulation, characterized in that, Includes the following steps: S1. Dissolve sodium acetate, aluminum nitrate, ferric nitrate, manganese sulfate and copper nitrate in deionized water in sequence, and continue to add the modified solution to form solution A. Dissolve citric acid in deionized water to form solution B. S2. Add solution B dropwise to solution A to obtain a mixed solution, and stir the mixture at 300-500 r / min at 60-90℃ for 4-5 hours to obtain a gel. S3. The gel is dried to obtain a precursor. The precursor is ground, pre-calcined, pressed into a sheet, and then calcined at high temperature to obtain an aluminum-doped layered sodium-ion battery cathode material. The modified liquid is prepared through the following steps: S11. Add the chloride product, trimethyl borate, and p-toluenesulfonic acid to anhydrous toluene and reflux at 100-110℃ for 5-6 hours. S12. After the reaction is complete, toluene and excess trimethyl borate are removed by rotary evaporation to obtain an intermediate. The intermediate is then dissolved in deionized water to obtain an intermediate solution. S13. Dissolve sodium tetrafluoroborate in deionized water and then add it dropwise to the intermediate solution. Stir at room temperature for 5-6 hours. After the reaction is complete, concentrate under reduced pressure at 40-50℃ to 30-40% of the original volume. Cool to 0-5℃ and let it stand to crystallize for 10-12 hours. Filter and wash the filter cake 2-3 times with deionized water. Dry under vacuum to obtain the modified ionic compound. Add the modified ionic compound to deionized water to obtain the modified solution. The chloride product in step S11 is obtained through the following steps: S111. After mixing choline chloride and ethylene glycol, add N-methylimidazole and 3-chloropropionic acid, stir for 5-10 min, add aluminum nitrate nonahydrate and stir until dissolved, and microwave at 90-95℃ for 2-3 h. S112. After the reaction is complete, add anhydrous ethanol to dilute, stir for 10-15 min, remove ethanol by rotary evaporation to obtain crude product, wash crude product with ethyl acetate 3-4 times, and dry under vacuum to obtain chloride product.

2. The method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation according to claim 1, characterized in that, In step S1, the mass ratio of sodium acetate, aluminum nitrate, ferric nitrate, manganese sulfate, copper nitrate, deionized water, and modified solution is 1:(0.02-0.15):(0.2-0.5):(0.3-0.6):(0.05-0.2):(5-15):(0.8-2), the mass ratio of citric acid to deionized water is 1:(15-20), and the mass ratio of solution A to solution B in step S2 is 1:(0.6-1.2).

3. The method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation according to claim 1, characterized in that, In step S11, the mass ratio of chloride product, trimethyl borate, p-toluenesulfonic acid, and anhydrous toluene is 1:(1.5-3):(0.05-0.15):(15-20).

4. The method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation according to claim 1, characterized in that, In step S12, the mass ratio of deionized water to intermediate is (10-15):

1.

5. The method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation according to claim 1, characterized in that, In step S13, the mass ratio of the intermediate solution, sodium tetrafluoroborate, and deionized water is 1:(0.4-0.8):(6-15), and the mass ratio of the modified ionic compound to deionized water is 1:(5-15).

6. The method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation according to claim 1, characterized in that, The mass ratio of choline chloride, ethylene glycol, N-methylimidazole, 3-chloropropionic acid, aluminum nitrate nonahydrate, and anhydrous ethanol in step S111 is 1:(2-4):(0.6-1.2):(0.7-1.3):(0.03-0.1):(20-25).

7. The method for preparing a high-performance layered sodium-ion battery cathode material with aluminum-driven lattice regulation according to claim 1, characterized in that, In step S3, the grinding time is 25-30 min, the sieve type is 200-250 mesh, and the pressure is 10-12 MPa; the pre-calcination temperature is 450-480℃, and the holding time is 3-6 h; the high-temperature calcination in step S3 is a two-stage process, specifically: first, the temperature is raised to 350-550℃ and held for 5-7 h, with a heating rate of 2-7℃ / min; then, the temperature is raised to 850-950℃ and held for 10-15 h.

8. A high-performance layered sodium-ion battery cathode material with aluminum-driven lattice modulation, characterized in that, It is prepared according to the preparation method according to any one of claims 1-7 above.

9. The application of the aluminum-driven lattice-controlled high-performance layered sodium-ion battery cathode material according to claim 8 in sodium-ion batteries.

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